In recent years, from the viewpoint of space saving, in place of a CRT type display conventionally and widely used, there have been widely used flat panel displays such as a liquid crystal display, a plasma display, an OLED display, and a field emission display. The OLED display is hard to up-sizing, and hence the OLED display is widely used for a display for a small device such as a mobile phone. The OLED display is fast in response rate and excellent in viewing angle compared with the liquid crystal display, and is small in power consumption compared with the plasma display. Thus, nowadays, the OLED display is expected to be put into mass production for large-screen television, and developments for larger OLED displays are advanced by various manufacturers.
A light-emitting element used for an OLED display deteriorates in quality through the contact of gasses such as oxygen and water vapor. Thus, a substrate used for the OLED display is required to have high gas-barrier property, and hence the use of a glass substrate is considered. However, when such a resin-based sealant as described in Patent Document 1 below is used for making the glass substrates adhere to each other, the gas-barrier property of the sealant may become insufficient. In that case, gasses such as oxygen and water vapor enter inside through the resin-made sealant during long-term use, leading to a problem that the light-emitting element has an aging degradation.
In order to solve the above-mentioned problem, Patent Document 2 below proposes that, in a case where glass substrates are sealed with each other, a light-emitting element is sealed by a glass frit with low melting point through a heat treatment. Patent Document 2 below describes that a flit composition including a glass portion which contains a base component containing SiO2, B2O3, and Al2O3 and at least one absorbing component (at least one of CuO, Fe2O3, V2O5, and TiO2) is subjected to sintering at about 700° C., thereby to seal the element.
However, the light-emitting element used for an OLED display is labile to high heat. Thus, when the frit composition described in Patent Document 2 below is used, the light-emitting element on the substrate may be destroyed through the sintering process at as high temperature as 700° C.